What are the similarities of diesel engine and petrol engine?

 The characteristics of bulkiness, noise and black smoke make many people have a bad impression on the diesel engine. After years of research and application of new technology, the current situation of modern 4stroke 6cylinder diesel engine is different from that of the past. Modern diesel engines generally adopt electronic control injection and common rail technology, which has made great breakthroughs in weight, noise and smoke. It has reached the level of gasoline engines.

Electronic control injection technology

The main difference between diesel engine and gasoline engine in electronic control injection is that the electronic control injection system of gasoline engine only controls the air-fuel ratio (the ratio of gasoline to air), while the electronic control injection system of high speed 6cylinder diesel engine adjusts the load by controlling the injection time.

The electronic control injection system of 4stroke electric starting diesel engine consists of three parts: sensor, ECU (control unit) and actuator. Its task is to control the injection system electronically to realize the real-time control of the injection quantity. The real-time measured parameters are input into the computer synchronously through the speed, temperature and pressure sensors and compared with the parameters stored in the ECU, so that the diesel engine can operate in the best condition.

In order to make the load regulation more accurate, the common rail technology is produced. Supercharging and intercooling technology is to compress the fresh air through the turbocharger, cool it through the middle cooler and then flow to the cylinder combustion chamber through the intake manifold and intake valve. The effective intercooling technology can reduce the supercharging temperature to below 50 ℃, which is helpful to reduce exhaust emissions and improve fuel economy.

Common rail technology

In the automobile high speed 6cylinder diesel engine generator, the high-speed operation makes the time of diesel injection process only a few thousandths of a second. The experiment shows that the pressure of high-pressure tubing varies with time and position. Due to the compressibility of diesel oil and the pressure fluctuation of diesel oil in high pressure oil pipe, the actual injection state is quite different from the plunger oil supply law specified by the injection pump. Sometimes the pressure fluctuation in the oil pipe will rise again after the main injection and reach the pressure that makes the needle valve of the injector open, which will reopen the closed needle valve and produce the phenomenon of secondary injection. In addition, the residual pressure in the high-pressure oil pipe will change and cause unstable injection after the injection cycle. This phenomenon is especially easy to occur in the low speed area. In order to solve the problem of fuel pressure change in powerful 12cylinder diesel engine, the modern diesel engine adopts a technology called "common rail".

Common rail technology refers to a kind of oil supply mode which completely separates the generation of injection pressure and injection process in a closed-loop system composed of high-pressure oil pump, pressure sensor and ECU. The high-pressure oil pump delivers the high-pressure fuel to the common oil supply pipe and precisely controls the oil pressure in the common oil supply pipe, which makes the pressure of the high-pressure oil pipe independent of the engine speed. The defect of traditional 4stroke turbocharger diesel engine will be reduced by reducing the fuel supply pressure with the change of engine speed. The ECU controls the fuel injection quantity of the injector, which depends on the fuel rail pressure and the opening time of the solenoid valve.